Boneyarding Metalua

Proposing that we toss Metalua into the boneyard. Reasons:

1) It is hard-coded to look for Lua & Luac binaries, which are
obviously now pointing at Lua (5.2). I tried tweaking those hard-coded
lines with inreplace and had some success, but it still broke on
finding Luac. It complies ‘successfully’, but it won’t do very much.

2) There’s been no stable Metalua release for 5 years.

3) The HEAD build hasn’t worked in at least 8 months because the github
has moved away from compile scripts in favour of becoming Luarocks.

4) Honestly, interest in Metalua seems to be pretty low. If nobody has
noticed the HEAD build has been dead for 8 months…?

I feel like we’d be better scrapping this and pointing people at the
new Luarocks available for Metalua, which are on versions 0.7.2-1
compared to our shipped 0.5-rc2.